Tumor Stem Cell Antigens as Consolidative Active Specific Immunotherapy

Abstract

Only 10% of metastatic melanoma patients survive 5 years, even though many can achieve substantial tumor reduction by surgical resection and/or radiation therapy and/or systemic therapy. An effective, nontoxic, consolidation immunotherapy could benefit such patients. We initiated a randomized trial to compare 2 promising patient-specific immunotherapy cell products. Patients had to have a diagnosis of metastatic melanoma and availability of an autologous melanoma cell line. Patients were stratified by whether their most advanced stage had been regional or distant metastases, and by whether they had measurable disease at the time of treatment, then they were randomized to receive irradiated autologous proliferating tumor cells or autologous dendritic cells (DC) loaded with antigens from such cells. Both products were injected subcutaneously in 500 µg of granulocyte-macrophage colony stimulating factor, weekly for 3 weeks and then monthly for 5 months. Patients in the 2 arms did not differ in baseline characteristics. All patients received prescribed therapy. Treatment was well tolerated. At the time of initial analysis, with no patients lost to follow-up, 50% of patients deceased, and all surviving patients followed for at least 6 months after randomization, survival is superior in the DC arm (hazard ratio, 0.27; 95% confidence interval, 0.098-0.729) with median survival not reached versus 15.9 months, and 2-year survival rates of 72% versus 31% (P=0.007). This trial provides evidence that a DC vaccine is associated with longer survival compared with a tumor cell vaccine, and is consistent with previous data suggesting a survival benefit from this patient-specific immunotherapy.